1. Field of the Invention
The present invention relates to a method of and apparatus for separating gold or other heavy metals from sand, ore, or other materials in which those metals occur.
2. Description of the Prior Art
Historically, gold miners have used a variety of methods and devices for removing gold from ore or sand in which that gold naturally occurs. A commonly used device which has been used for more than a century is a riffle board. The riffle board has ridges which are designed to trap and retain gold, as sand in which that gold resides is washed over the board. Typically, the riffle board was placed in a stream to allow constant washing with water as sand was placed on the board by the miner. The relatively heavy metal tended to fall out of the sand and be retained in the ridges of the riffle board, as relatively lighter-weight sand was washed down the stream. Although inefficient and capable of processing only small amounts of sand at a time, the riffle board provided gainful employment for many a gold miner.
Over the course of time, other devices have been invented to separate gold from other materials. For example, U.S. Pat. No. 289,018, granted in 1883 to Miller, describes an ore concentrator which involves placing materials in a pan and subjecting that pan to a blow, so that heavier particles such as gold would advance to the point “where the blow is given”, leaving other materials to be discharged.
A double sluice, over which sand and water flows first one direction and then another, is described in U.S. Pat. No. 4,319,985 to Hibbard. The device described in U.S. Pat. No. 4,860,874 to Winderl relies on vibration of a trough to concentrate ore.
A device typically known as a “California Gold Hound” is used to remove black sand from concentrate or gold from placer materials. In an example of this device taught by U.S. Pat. No. 5,275,294 to Krenzler, a separator pan having a spiral rib is set in a stream, and the pan is rotated, causing particles of gold introduced into the pan to be moved inwardly into a receptacle at the center of the pan. U.S. Pat. No. 2,053,802 to Nicol teaches a two-step process for removing minerals from black sand or similar material using a rotating drum, potentially positioned in a stream to receive water. The Nicol device has circumferential cross riffles for collecting gold and longitudinal riffles, arranged perpendicular to the cross rifles, for collecting and removing gold. A feed chute is positioned to add material into the drum at an open end, potentially disturbing separated gold before it can be collected.
Similarly, U.S. Pat. Nos. 4,265,743 and 4,347,130, both to Younge, describe rotating sluice boxes for removing gold or other relatively heavy particles from placer gravel. These devices rely on centrifugal force to force relatively heavy particles to be separated from waste materials. U.S. Pat. No. 4,071,143 to Richan teaches an apparatus with a rotatable conical cap, curving sides, and a vertically extending riffle through which flows an ore-water slurry to capture heavy metals and dispose of tailings. Currents of air are blown over sand containing gold to separate the gold in U.S. Pat. No. 4,642,180 to Kaufman.
Devices used for related purposes have also been developed. U.S. Pat. No. 7,168,568 to Wise describes a device for separating non-magnetic minerals from a source containing both magnetic and non-magnetic material. U.S. Pat. No. 3,761,132 to Grable teaches an apparatus for upwardly displacing soil by delivering fluid under pressure underground, with the potential auxiliary purpose of removing upwardly displaced precious metal particles.
While each of these devices is useful for its intended purpose, none enables a user to easily transport a machine to a site of sand or other ore naturally containing metals, which machine can be utilized to efficiently remove and retain heavy metals from significant quantities of sand.